Nitrate selective amidine ion exchange resins

Abstract

Water swellable ion exchange resins comprising a polymeric matrix and amidine groups are described together with their synthesis. The preferred amidine groups are nitrate selective and methods of selectively removing nitrate from water are also described.

I claim: 
     
       1. A water-swellable, ion exchange resin comprising a cross-linked vinyl polymeric matrix and amidine groups chemically bonded to the matrix and which have the formula ##STR6## where Q represents hydrogen or C 1-4  alkyl and both of R represent C 1-6  alkyl or one R is C 1-6  alkyl and one R is benzyl, which in total provide up to 12 carbon atoms. 
     
     
       2. A resin according to claim 1 in which the matrix is a vinyl polymer cross-linked with divinyl benzene. 
     
     
       3. A resin according to claim 1 in which the radicals R are the same or different and represent C 1-6  alkyl and the radical Q represents hydrogen. 
     
     
       4. A resin according to claim 1 in which the radicals R are the same or different and represent methyl, ethyl, a propyl, or a butyl and Q is hydrogen. 
     
     
       5. A resin according to claim 1 in which one radical R is selected from methyl, ethyl, propyl and butyl, and one radical R is a butyl. 
     
     
       6. A resin according to claim 1 in which one radical R is ethyl and the other is butyl. 
     
     
       7. A resin according to claim 1 in which the total number of carbon atoms in the two groups R and Q is 4 to 9. 
     
     
       8. A resin according to claim 1 in which the total number of carbon atoms in the groups R and Q is 5 to 7. 
     
     
       9. A method of selectively removing nitrate ion from water comprising contacting the water with a water-swellable ion exchange resin comprising a cross-linked vinyl polymeric matrix and amidine groups chemically bonded to the matrix and which have the formula ##STR7## where Q represents hydrogen or C 1-4  alkyl and both of R represent C 1-6  alkyl or one R is C 1-6  alkyl and one R is benzyl, which in total provide up to 12 carbon atoms. 
     
     
       10. A method according to claim 9 in which the total number of carbon atoms in the groups R and Q is 4 to 9. 
     
     
       11. A method according to claim 9 in which the said number is 5 to 7. 
     
     
       12. A method according to claim 9 in which one radical R is ethyl and the other is butyl. 
     
     
       13. A method of making a resin according to claim 1 comprising reacting crosslinked polyacrylate with a primary amine to form the corresponding polyacrylamide, halogenating this to form the corresponding polyimidoyl halide and reacting this with a primary or secondary amine or ammonia. 
     
     
       14. A method according to claim 9 in which the radicals R are the same or different and represent C 1-6  alkyl and the radical Q represents hydrogen. 
     
     
       15. A method according to claim 9 in which the radicals R are the same or different and represent methyl, ethyl, a propyl, or a butyl and Q is hydrogen. 
     
     
       16. A method according to claim 9 in which one radical R is selected from methyl, ethyl, propyl and butyl, and one radical R is a butyl.